Multiple governing system for turbine with automatic transfer



J. M. BAKER MULIPLE GOVERNING SYSTEM FOR TURBINE Oct. 14, 1952 WITHAUTOMATIC TRANSFER Flled Jan. 4, 1952 IKN Inventor: Jack M .BaKe1^,

be @FM4 dwg His Attorrweg Patented Oct. 14, 1952 MULTIPLE GOVERNINGSYSTEM FOR TUR- EINE WITH AUTOMATIC TRANSFER Jack M. Baker, SouthPeabody, Mass., assignor to General Electric Company, a corporation ofNew York Application January 4, 1952, Serial No. 264,928

(Cl. ZBO-4) 7 Claims.

This invention relates to hydraulic-mechanical governing systems forprime movers such as steam turbines, particularly to governing means fora non-condensing type steam turbine having two or more modes ofgoverning, and arranged to provide automatic transfer from one type ofgoverning to another.

In industrial plants such as paper or textile mills, it is usually foundmost economical to use extraction or non-condensing type turbines forgenerating electricity and furnishing steam for various process andheating purposes. Since the reliability of the supply of electricalenergy is of substantial importance in connection with such continuousindustrial processes, the mills turbine-generator unit will ordinarilybe interconnected with an electric power distribution network so either,or both together, can furnish the electrical energy needed in the mill.The steam used for process purposes will first drive the turbine togenerate electrical energy, and any power required in the mill over andabove the amount generated by the turbine will be supplied from thepower distribution network. When thus connected to an external powerdistribution network, the speed of the mills turbine-generator unit willbe determined by this electrical interconnection with the otherturbine-generators supplying the network. When thus interconnected withthe network, the mills turbine will be governed by suitable devicessensitive to conditions other than speed, for instance, means arrangedto hold constant the pressure of the exhaust steam used for processpurposes, regardless of variations in the rate of iiow thereof.

In the event of a fault in the external electrical power network, orwhen the tie-line circuit breaker connecting the mills turbine-generatorto the network is opened for any reason', it is then necessary that themills turbine be so governed as to hold the speed constant, in orderthat the frequency ofthe electrical energy sup'- plied to the electricmotors driving the mill will be maintained essentially constant. Itwillof course be appreciated by those familiar with such power-plantsthat any slightest variation from the preselected desired speed mayresult in serious breakage in the thread of a textile mill or the web ina paper mill, etc. For such f service, it is absolutelyessential that',in the event of a disturbance in the power network, or failure of theelectrical energy supply'from the network, that substantiallyinstantaneous and automatic conversion of the mills turbine-governingsystem shall be effected, with no important disturbance in the frequencyof the electrical energy supplied to the mills motors.

Accordingly, the purpose of the present invention is to provide animproved governing system i'or a turbine supplying both process steamand electrical energy, with automatic means for quickly changing thegovernor from one mode of operation to another.

A further object is to provide a turbine governor of the type describedwhich will ordinarily hold constant some operating condition other thanspeed, such as exhaust pressure or 'turbine load, but which willautomatically convert the governing system to hold speed constant uponoccurrence of a preselected event such as failure of the vsupply ofelectrical energy from an external power distribution network.

Other objects and advantages will become apparent from the followingdescription taken in connection with the accompanying drawing, in whichFigure 1 is a diagrammatic representation of a steam turbine governingsystem incorporating the invention"y and Figure 2 is an alternate formof one of the governing sub-combinations.

Generally stated, the invention is practiced by employing a knownv typeof speed governor with special speed corrector means adapted to effectisochronous operation (no netspeed change as load varies) in combinationwith other governing means for holding constant some other operatingcondition, such as turbine load or exhaust steampressure, with automaticmeans for disabling certain of the governing mechanisms and transferringcontrol to the speed governor, special means being provided to reducethel time required for the transfer and to insure stability during thetransition period.

Referring now more particularly tothe drawing, the governing system isillustratedv as "embodied in a hydraulic-mechanical arrangement forcontrolling the flow of motive fluid through steam inlet conduit I tolthe multi-stage turbine 2'. Motive iiuid flow is controlled by asuitable throttle valve 3 positionedv by hydraulic motor 4. rthe turbine2r supplies process steam through exhaust conduit 5 and drives agenerator 6 connected to supply electrical energy to a load indicated at7. In a mill for manufacturing paper or textiles, this load would ofcourse represent electric motors driving the paper or textile machinery.Load 'I isI also connected by' a tie-line indicated at 8 to an externalpower distribution network 9 supplied by a plurality of turbinegenerators, one of which is indicated at I0. The loa-d 'I may bedisconnected from the network 9 by a circuit breaker indicated at II.

Generally speaking, the turbine governing system comprises aconventional speed governor indicated at I2, speed corrector servomechanism I3 for effecting isochronous speed regulation, a pressuregovernor I4, a speed-resetting servo mechanism I5, and a plurality ofsolenoid operated dump valves I6, I'I, I8, connected to be energizedsimultaneously from a suitable power source by an automatic transferrelay I9 when the circuit breaker I I is opened. In the present case,the relay I9 is shown as having a current responsive coil lea adapted tohold the bridging contacts ISb in open position when current is iiowingin the tie-line circuit 8, but permitting spring I9c to move contactsISb to closed position so as to energize solenoids I6, I'I, I3 when thetie-line current fails. It will of course be understood that any otherequivalent devices, such as a frequency-responsive relay sensitive tothe frequency in the network, may be used for energizing these solenoidsautomatically when circuit breaker' EI is tripped to the open condition.

The hydraulic speed governor I2 is of conventional arrangement, andincludes a speed responsive ily-ball governor I2a, or the equivalent,connected to position a hydraulic pilot I2b. The pilot is arranged toslide longitudinally in a pilot bushing I2C. As will be apparent fromthe drawing, speed governor I2 is arranged to regulate the iiow ofoperating liquid from a supply conduit 2t to hydraulic motor 4 by way ofconduit 2 I. It will be appreciated by those skilled in the art thatthere is a certain amount of leakage in the hydraulic motor 4 and pastpilot land I2b to drain port I2f, so that at least a small amount of oilmust be supplied continuously through conduit to maintain throttle valve3 in a given desired position.

The arrangement and operation of the speed governor I2 are well known inthe art. If the speed should rise above the preselected value, theilyball governor |20, pulls pilot I2bdownward1y to establishcommunication between hydraulic motor 4 and the drain conduit I2f, sovalve rod 3a descends to close valve 3 somewhat. Conversely, a decreasein speed raises pilot I2b to admit more liquid from conduit 20 to raisevalve rod 3a. It is to be noted that the condition of speed governor I2shown in Figure l is that occurring when the governing system is holdingconstant exhaust steam pressure, there being a substantial flow ofhydraulic operating liquid as indicated by arrow I2e, under the controlof the pressure governor I4, as described more particularly hereinafter.When the governing system is converted so as to hold constant speed,pilotv I2b is positioned relative to bushing I2C so that the pilot justcovers the supply and drain ports in the bushing. Then any furthermovement of the pilot in one direction will immediately uncover thesupply port to open steam valve 3, while a movement in the otherdirection from the aligned position will uncover the drain port to closevalve 3.

In order to establish the speed setting of governor I2, pilot bushingI2C is connected to be positioned by a speed setting lever 22. Thelefthand end of lever 22 is adapted to be positioned by a follow-uplever 23 supported on a Xed fulcrum. The other end of lever 23 isconnecte-d by a link 24 to a follow-up lever 25, the lefthand end ofwhich is pivoted to the valve actuating rod 3a. It will be appreciatedby those skilled in the art that when movement of valve spindle 3a iseffected by speed governor I2 supplying operating liquid to hydraulicmotor 4, the resulting movement acts through lever 25, link 24, andlevers 23 and 22 to reposition bushing I 2c in a direction todiscontinue or diminish the supply of operating liquid to motor 4.

In order to alter the desired speed which governor I2 will maintain, therighthand end of speed setting lever 22 is adapted to be positioned by asynchronizing device 2G, which includes a threaded rod 26a, adapted tobe rotated by the manual handwheel 25e, or remotely by a suitableelectric positioning motor (not shown). The righthand end of speedsetting lever 22 is pivoted to a bushing 26h threadedly received on theadjusting spindle 26a and adapted to be positioned vertically within arange determined by limit stops 26e, 26d. rl`hese stops may take theform of suitable threaded bushings arranged to be adjustably secured tothe spindle 25a. The upper stop 26e is the low speed stop, while theother stop 26d is the high speed stop. It will be observed that thebushing 26h is shown against the high speed stop 26d, representing thecondition when the governing system is holding constant exhaustpressure.

For automatically setting the synchronizing device 26 so that governorI2 will hold a preselected speed, there is provided a hydraulic speedreset servo shown at I5 as comprising a piston I5a biased downwardly bycoil spring I5?) to a limiting position determined by an adjustable stopI5c. When the governing mechanism is operating to hold constant exhaustpressure, speed reset piston I5a is held in its upper-most position (asshown in the drawing) by hydraulic oil pressure supplied from a suitablepump (not Shown) through conduit I5d containing a flow restricting oriceI5e. The oil pressure which normally holds piston I5a at the top of itsstroke may be relieved either manually by opening a drain valve I5f orautomatically by the solenoid valve I8, which includes a flow controlmember I8@ adapted to be pulled upwardly by solenoid IBD to establishcommunication between conduit IEd and drain port I8c. It will beapparent that, when the hydraulic liquid in servo I5 is dumped, byeither the automatic valve I8 or the manual valve I5f, the liquid willescape faster than it can be supplied through orifice I5e, with theresult that spring I5b biases piston I5a to the bottom of its stroke, asdetermined by engagement of stop I5c with the housing of the speed resetservo. rihus the speed reset servo I5 eiiects positioning of thesynchronizing screw 26a through lever I5g so as to cause governor I2 tohold a preselected speed, which speed is determined by suitablepositioning of the adjustable stop I 5c of the speed reset servo.

When in normal operation, with tie-line circuit breaker I I closed sothat the speed of turbine 2 is determined by its electricalinterconnection with the power distribution network 9, the supply ofmotive fluid to turbine 2 by the throttle valve 3 will be regulated inaccordance with some other operating condition, for instance thepressure of the process steam being delivered through turbine exhaustconduit 5. To this end, the process steam pressure is communicated byconduit 21 to the pressure responsive governor I 4a. The details ofgovernor I 4a are not material to an understanding of the presentinvention, but this device may be, for instance, in accordance with thepressure governor disclosed in United States Patent 2,253,963 issued inthe name of F. H. Van Nest on August 28, 1941 and assigned to the sameassignee as the present application. It need only be noted here thatgovernor Ida receives hydraulic operatingliduid through conduit `I 3band contains hydraulic motor means adapted to position an output memberMc in accordance with the dictates of the pressure signal receivedthrough conduit 27, The pressure which governor I4a will hold isdetermined by suitable adjustment of the hand-wheel Idd.

The output member |40 of pressure governor I4a is pivoted to one end ofa pressure governor lever I4f. An intermediate portion of lever I4f isconnected to position pilot valve I4g which regulates the supply ofhydraulick operating liquid through conduit 29 to the speed regulatingpilot I2. The lefthand end of lever Idf is connected to be positioned bythrottle valve actuating rod 3a., in order to provide the follow-upeffect required.

For disabling the pressure governor I4, when it is desired to operatethe system so as to hold constant speed, the pressure signal in conduit.21 may be destroyed manually by opening a dump valve 21a, orautomatically by the solenoid valve I'I. As can be seen in Figure 1, thevalve II comprises a flow control member IIa adapted to be pulledupwardly by solenoid IIb in order to establish communication betweenconduit 21 and drain port' llc.

The stability and speed response of the pressure governor I4 may beadjusted by means of a manual shut-off and throttling valve 21h inconduit 21. Excessive loss of steam through conduit 21 is prevented by afixed orifice 21e. Thus, it Will be apparent that the pressure signal isprevented from reaching the governor Illa whenever manual valve 21a orautomatic valve I'I is actuated to bleed away the steam faster than itcan be supplied past the valve 2lb and orice 21C. When the pressuregovernor Ida is thus rendered inactive, the output rod I4c will becaused to move to the bottom of its stroke, so that pilot I4g will be atits lower-most position to effect free communication of hydraulicoperating liquid through conduit 20 to speed governor'IZ.

The function of the speed corrector servo I3 is to produce a modifyingeffect on the action of speed governor I2 so that it will hold constantspeed with substantially zero regulation, which is dened as thevariation in speed permitted by the governor when the load varies fromminimum to maximum. Without the aid of speed corrector I3, the normalregulation of a governor of the type shown at I2 will be on the order of4%. However, this is not sufliciently close to isochronous for drivinggenerators supplying electrical energy for paper or textile mills.Accordingly, the speed corrector I3 produces steadystate regulation onthe order of plus or minus .1 The speed corrector shown diagrammaticallyat I3' is generally of a type known previously in the art, speedcorrectors of this general type being shown for instance in the patentsof R. G. Standerwicl, 1,629,318 and 1,629,319, issued May 17, 1927, and1,810,627 issued June 16, 1931, also the U. S. patent of E. D.Dickinson, 1,976,659, issued October 9, 1934, all assigned to the sameassignee as the present application.

As shown, the speed corrector I3 comprises a hydraulic speed correctorpiston I3a. biased downwardly by a weight I3b and connected to amidpoint of follow-up lever 25 by an intermediate lever I3c supportedkon a fixed fulcrum as shown. The upper limiting position of'piston I3a.is established by an adjustable stop I3d adapted to' engage leverI3'cwhen the limit is reached. The speed corrector piston I3a ispositioned by hydraulic liquid supplied through conduit I3e ascontrolled by pilot I3f, which is connected to lever I3g pivoted at oneend to link 24 and supported on a xed fulcrum, as shown. The kother endof lever I3g is adapted to be positioned by engagement with adjustablestops I3h, I3lc threadedly received on the spindle of pilot I3f. Thefunction of stops I3h, I3Ic is to adjust the relative position of pilotI3fand bushing I2c through levers I3g, 24, 23 and 22 for the value ofisochronous speed to be held and to permit taking the speed corrector I3out of service altogether. By turning stop nut I3h, the pilot I3 f maybe displaced downwardly to admit oil to hold piston I3a in its uppermostposition, with lever I3c against stop I3d, in which condition the speedcorrector is inoperative. In this connection it will be seen that a coilspring I3m biases pilot I3f downfso stop 13h is held against the forkedend of lever I3g. When the speed corrector servo is intended to operatefor isochronous governing, these stops are in engagement with theopposite sides of lever I3g, as shown.

In accordance with the invention, special means are provided fordisabling the speed corrector servo I3 when the system is operating tohold constant exhaust pressure, and automatic means are provided tobring the speed corrector into operation after a pre-selected timeinterval, when operation is converted to speed governing. This automaticcontrol device for speed corrector I3 comprises a. two-position flowrestricting valve 28, which may be in the wide open position (as shown),or it may be in any preselected position between wide open position andits minimum area position, when the system is holding constant pressurewith the speed corrector servo I3 inoperative, and which isautomatically brought to its minimum area position in order to renderthe speed corrector servo operative when the system is converted to holdconstant speed. The flow restricting valve 28 must be in its minimumflow position for satisfactory operation with the speed corrector inservice. However, if it were to remain in the minimum position prior toand during the transfer from exhaust` pressure control to speedcorrector control, the elapsed time interval for completion of theAtransfer to isochronous speed governing would be on the order of 15 to30 seconds. In accordance with the invention, means are provided forholding the flow restricting valve open and to automatically close valve28 to its minimum area position when operation is converted to speedgoverning, which automatic means reduces the elapsed time interval forcompletion of the transfer to as low at l/2 to 11,4; seconds.

'Ihe positioning means for valve 28 comprises a lever 29 connected byrod 39 to a hydraulic piston 3| which is biased downwardly by a spring32, the lower-most position thereof (corresponding to the minimumeffective area of valve 28) being determined by an adjustable stopthreaded on spindle 30 and adapted to engage the housing 34. Normally,hydraulic pressure supplied past a flow restricting orifice 35 inconduit 36 holds piston 3I in its upper-most position (as shown) againstthe bias of spring 32. The open position of valve 28, when piston 3| isin uppermost position, may be adjusted to suit the requirements of theparticular system in which the turbine is installed, by any suitablemeans for varying the lengthof rod 28a, such asv the threaded bushingshown in the drawing. Piston 3| is permitted to descend under theinfluence of spring 32 when pilot I6 is pulled upwardly by solenoid I6aso as to establish communication between conduit 3S and the drain portIBD. A manual throttling valve 31 in conduit 36 between the hydraulicpiston 3| and dump valve I6 permits adjusting the rate at which piston3| will descend. This has the important function of determining the timeinterval required for the throttling valve 28 to move from its maximumarea position to the minimum area position when the speed correctorservo goes into operation.

Having described the various sub-combinations which comprise thecomplete governing system shown in Figure 1, the overall operation is asfollows.

With the tie-line circuit breaker II closed, the electricalcharacteristics of the network 9 determine the speed of turbine 2, andthe position of the parts will be as shown in Figure 1 for governing theturbine throttle valve 3 so as to maintain process steam pressure inconduit constant. The value of this pressure is regulated by thehandwheel Idol of pressure governor I4a, which governor regulates thepilot valve |49. Since the speed reset servo piston I5a is held in itsuppermost position by hydraulic pressure, the speed setting screw 28awill be maintained in its lowermost position, with the result that speedgovernor bushing I 2c is positioned downwardly suilciently to establishfree communication as indicated by arrow I2c. Thus the pilot |49associated withk pressure governor I4 is free to regulate the ow ofoperating liquid to hydraulic motor 4, without any interference fromspeed governor l2.

It is a known characteristic of hydraulic speed correctors of thegeneral type shown at I3 (as described in the above-identifiedStanderwick Patent 1,629,318) that they perform their speed correctingfunction only when there is a phaselag" introduced-by having a flowrestriction between the pilot valve |32* and the hydraulic piston |3a,and when hydraulic piston I3a is physically able to position fulcrum Xand thereby position bushing I2c through levers 25, 23 and 22 and link24 so as to cause bushing I2c to be line to line with pilot valve I2b,so as to control oil pressure in conduit 2| and thus position motor 4.In order that pressure governor I4 through pilot valve Idg will havecomplete control of the turbine steam iiow for maintaining constantexhaust pressure, synchronizing screw 26a is turned so that trunnion 26his against high speed stop 26d and bushing I2c is in its lower-mostposition permitting the oil to ow as shown at I2c. For this position ofscrew 26a it is impossible for the hydraulic piston I3a to positionfulcrum X so as to put bushing I2c line to line with pilot valve I 2bdue to stop |3d. Therefore, hydraulic piston I3a will maintain lever |30against stop I 3d and thus fulcrum X will be fixed in space at all timeswhen pressure governor I4 through pilot Mg is in control of the turbine.Also, the flow restriction between the pilot valve I3f and hydraulicpiston I3a required for proper functioning of the speed corrector servois provided by valve 28. Thus the speed Vcorrector is inoperative whenvalve 28 is wide open, as shown in the drawing; and therefore the speedcorrector servo I3 has no eiiect on the operation of the system when thepressure governor I4 is controlling the turbine.

If now some failure should occur in the power distribution network 9causing tie-line breaker II to open automatically, or if breaker IIshould be tripped open manually for any reason, the failure of currentin solenoid I9a will cause contacts |9b to close, thus simultaneouslyenergizing solenoid valves I6, I1, I8. The resulting loss of thepressure signal in conduit 21 -immediately disables the pressuregovernor I4a and positions pilot valve |49 downwardly so as to permitfree now of pressure oil to conduit 2D. Simultaneously, the speed resetservo piston I5a Adescends and lcauses the synchronizing screw 26 torise, thus elevating bushing I2c so as to bring the ports therein intoalignment with the lands of pilot I2b, so that the speed governor takesover control of hydraulic motor 4. As will be appreciated by thoseskilled in the art, the normal operating condition for governor I2, whenin control of the turbine speed, is with one of the lands of the pilot I2b in aligned or line-to-line" relation with the supply port in bushingI2c, with the other land :aligned with dump port I2 f.

Meanwhile, solenoid valve Ilia has also established communicationbetween conduit 36 and drain port IGb, with the result that the piston3| begins to descend, but at a preselected rate as determined by theadjustment of valve 31. This adjustment, for instance, may be So setthat it requires on the order of 1/2 to 11/2 seconds for the adjustablethrottling valve 28 to move from its open position to the minimum areaposition, when solenoid valve I5 opens. The result is that, when thespeed governor I2 nrst takes over, it reacts quickly (with valve 28 wideopen) to establish the speed preselected by the speed reset servo I5,the speed v. load regulation at the instant or" change-over being trulyzero. This prompt response of speed governor I2 insures that the speedof turbine 2 will experience the :absolute minimum deviation from thenormal speed required by the load devices 1. However, the system wouldnot be sufficiently stable if this conditon were to persist for anylength of time. Therefore, the effect of the progressive closing of flowrestriction 28 is to provide the phase lag necessary for stableoperation on speed corrector control, and to change the degree ofregulation of speed governor I2 from zero -to its normal value of 4% oninstantaneous load changes, with zero regulation (within 0.1%) upongradual load vchanges taking several minutes to effect. The adjustablevalve 31 will of course be positioned as found necessary in service so-as to achieve suiiiciently quick response of speed governor I2 when theautomatic transfer relay I9 trips, yet at the same time bringing thespeed corrector servo I3 into operation sufficiently promptly as toobtain the desired isochronous governing.

Thus the system effectively permits automatic changeover from pressuregoverning to speed governing with minimum chance of disturbance in thespeed lof the load devices While the above description indicates how theinvention may be applied to a governing system arranged to convert fromexhaust pressure governing to speed governing, alternate governingcomponents may be substituted for the pressure governor I4. In thisconnection, Figure 2 represents a load limit governor 38 comprising anadjustable stop in the form of a lever 39 having an end portionV 39aadapted to be engaged by an abutment 3b secured to throttle valveactuating rod 3a. The position of the stationary abutment 39a is`adjusted by a screw 4U which may be rotated manually by the handwheel4I, or remotely by. la positioning motor (not shown). In

norm-al operation, with the tie-line circuit breaker I I closed so thatthe speed yof turbine 2 is determined by its electrical interconnectionwith the network. Si, the stop 39a will be positioned as shown in Figure2 so that throttle valve rod 3c cannot move in the opening directionpast a limiting position determined by the engagement of abutment 3bwith the stop 39a. Since the load on the turbine is a function of themovement of valve rod 3a, the abutment 39a establishes a load limit forthe turbine.

It is necessary to remove the limiting effect oi abutment 39a when thesystem is rconverted to speed governing, `and to this end a hydraulicpiston 42 is connected to Ipull adjusting screw 4i) downwardly so as tomove abutment 39a up- Wardly to such :an extent that it no longerest-ablishes a limiting -position for abutment 3b. As will be apparentin Figure 2, piston 42 is biased downwardly by coil spring 43 and isnormally held in uppermost position by hydraulic pressure establishedunder the pis-ton by supply of hydraulic liquid through a conduit 44containing a dow restriction 45. Piston 42 may be caused to descendeither manually by opening the drain valve 46 or automatically when thesolenoid 41 is energized to raise pilot 48 so that conduit 44communicates with drain conduit 49.

It will be obvious to those skilled in the rart .how the load limitarrangement shown in Figure 2 may be substituted for the pressureg-overnor i, in which event the solenoid 41 would also be connected tobe energized by the automatic transfer relay l 9 in Figure 1.

It will also be apparent to those familiar with turbine governor designthat the load limit governor shown in Figure 2 may be incorporated in agoverning system which also has a pressure governor i4 as shown inFigure 1. Then if it is desired to operate on the pressure governor, thedisabling valve 46 of the load limit governor will be open-ed, Whereasif it were desire-d to operate on the load limit governor, the valve 21aofthe pressure governor would be opened.

Thus, broadly, the invention comprises means for operating on any one ofseveral difierent governing devices, with automatic means fortransferring to speed control, with the speed corrector servo i3 beingbrought into operation after preselected 'time interval has elapsed.Without the invention, a time interval of on the order of 30 seconds mayelapse, when switching to speed governing, before the system settlesdown to stable isochronous operation; While with the invention thisinterval is reduced to a value between 1/2 to 11/2 seconds.

Still other changes and substitutions of equivalents will be apparent tothose familiar with such turbine governing systems; and it is desired tocover by the appended claims all such modifications as fall Within thetrue spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. In a governing system for a prime mover having a throttle memberadapted to regulate the supply of motive iiuid thereto with motor meansfor establishing the position of the throttle, the combination ofisochronous speed governor means connected to control the throttlemotor, and other governing mechanism adapted to control the positioningof the throttle member in normal operation, means for isabling saidother governing mechanism, said isochronous speed governor comprising aspeed-responsive device adapted to position the throttle motor 'tomaintain constant speed, linkage 'meansconnected to the throttle memberto produce afollovv-up effect 'on the speed governor, and speedcorrector means connected to said'linlrage to modify the action of thespeed governor tor eifi et isochronous governing, said speed correctorincluding second hydraulic motor means with pilot valve means adapted toregulate the supply of operating liquid thereto to eiiect the speedcorrecting lfunction, conduit means oonnecting said pilotto said secondhydraulic motor and including variable flow restricting means forlimiting the rate of supply of operating liquid to the second motor,said flow restricting means having an open position and a minimum flowposition, third 'motor' means for moving said flow restriction from itsopen position to its minimum flow position at a preselected rateoitravel, and means for simultaneously 'effectingactuation of saidldisabling vmeans for the other governing mechanism and eiiectingactuation of said third motor to render the speed corrector operativeafter a preselected interval.

2. A governing system for a steam turbine prime mover in accordance withclaim 1 in which the other governing mechanism is a pressure responsivegovernor adapted to hold constant the pressure of steam exhausted fromthe turbine.

3. A governing system for a steam turbine prime mover in accordancewithclaim l inwhich the other governing mechanism is a load limitgovernor having an adjustable stop for determining a limiting positionyfor the throttle member, with means rfor automatically removing saidstop when the system is converted to speed governing.

fi. In a governing system :for a prime mover having a throttle memberadaptedto regulate the supply of motive fluid thereto and motor meansfor establishing the position of the throttle, the combination ofisochronousspeed governor means adapted to control the throttlepositioning motor, iirst servo mechanism for automatically determiningthe speed to be `held by the speed governor, other governing mechanismadapted to control the positioning or the ,throttler member 'in normaloperation, second servo means for disabling said other governingmechanism, the isochronous speed governor comprising a speed responsivedevice adaptedto position the throttle motor to hold a speed determinedby said first servo mechanism, linkage means connected to the throttlemember to produce a follow-up effect on the speed governor, and speedcorrector means connected to said linkage to modify the action of thespeed governor to effect isochronous governing, said speed correctorincluding a second hydraulic motor with a pilot valve adapted toregulate the supply of operating liquid thereto to effeet the speedcorrecting function, conduit means connecting said pilot and secondhydraulic motor and including variable flow restricting means forlimiting the rate of supply of operating liquid to the second motor,said flow restricting means having an open position and a minimum flowposition, third servo means for causing said flow restricting means tomove from its open position to its minimum flow position at apreselected rate of travel, and means for simultaneously effectingactuation of said rst servo mechanism to establish the speed setting ofthe isochronous governor and effecting actuation of said second servomechanism for disabling the other governor and effecting actuation ofsaid third servo mechanism to render the speed corrector operative aftera preselected interval.

5. In a governing system for a prime mover having a throttle memberadapted to regulate the supply of energy thereto and motor means forestablishing the position of the throttle, the combination ofisochronous speed governor means connected to control the throttlepositioning motor, rst servo mechanism for automatically setting thespeed to be held by the speed governor, other governing mechanismadapted to control the positioning of the throttle member in normaloperation, second servo mechanism for disabling said other governingmechanism, the isochronous speed governor including a speed responsivedevice connected to position the throttle motor to hold a speeddetermined by said first servo mechanism and speed corrector meansconnected to modify the action of the speed governor to effectisochronous governing, said speed corrector including third servo meansfor placing the speed corrector into operation at a preselected rate,and means for simultaneously effecting actuation of said first servomechanism to establish the speed setting of the isochronous governor andalso effecting actuation of said second servo mechanism to disable saidother governing means and effecting actuation of said third servomechanism to render the speed corrector fully operative after apreselected time interval.

6. In a governing system for an elastic fluid turbine having a throttlevalve for regulating the supply of motive uid thereto and motor meansfor establishing the position of the throttle valve, the combination ofisochronous speed governor means connected to control the throttle valvepositioning motor, a rst speed setting servo mechanism connected to thespeed governor to establish the speed to be maintained thereby, othermechanism adapted to control the positioning of the throttle member inaccordance with an operating condition other than speed in normaloperation, second servo mechanism for disabling said other governingmechanism, the isochronous speed governor comprising a speed responsivedevice connected to position the throttle motor to hold a speeddetermined by said first servo mechanism, linkage means connected to thethrottle valve to produce a followup effect on the speed governor, andthird hydraulic speed corrector servo mechanism connected to saidlinkage to modify the action of the speed governor to effect isochronousgoverning, the hydraulic speed corrector including fourth hydraulicmotor means with a pilot valve adapted to regulate the supply ofoperating liquid thereto to effect the speed correcting function,conduit means connecting said pilot and fourth hydraulic motor andincluding variable ow restricting means for limiting the rate of supplyof operating liquid to said fourth motor, said flow restricting meanshaving an open position and a minimum flow position, fifth hydraulicservo mechanism for causing said ow restricting means to move from itsopen position to its minimum flow position at a preselected rate oftravel, and means for simultaneously effecting actuation of said firstservo mechanism to establish the speed setting of the isochronousgovernor and effecting actuation of said second servo mechanism fordisabling the other governing means and effecting actuation of saidfifth servo mechanism to render the speed corrector operative after apreselected time interval.

7. Multiple governing means for an elastic fluid turbine type primemover in accordance with claim 6 in which the turbine drives a generatorinterconnected with an electric power distribution network by a tie-lineincluding a circuit breaker for disconnecting the prime mover from thenetwork and the means for simultaneously effecting actuation of saidservo mechanisms comprises solenoid-operated pilot valves connected tobe simultaneously energized by a relay responsive to characteristics ofthe tie-line current.

JACK M. BAKER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,629,318 Standerwick May 17,1927 1,629,319 Standerwick May 17, 1927 1,759,763 Standerwick May 20,1930 1,810,627 Standerwick June 6, 1931 1,841,425 Taylor s- Jan. 19,1932 1,969,526 Rosch Aug. 7, 1934 1,976,659 Dickinson Oct. 9, 19342,253,963 Van Nest Aug. 26, 1941

